This invention relates to a magnetism prevention structure of a motor assist apparatus for a vehicle, and particularly to a magnetism prevention structure of a motor assist apparatus for a vehicle, which can shield various engine components from magnetic flux and electric wave noise generated by an electric motor without having to arrange for affecting magnetism prevention utilizing other components. The magnetism prevention structure of this invention can reduce the number of assemblies and the number of assemblies to assemble, and can therefore reduce costs.
With respect to vehicles, there is a so-called hybrid vehicle, which includes an electric motor (motor), driven by electricity and directly connected to an engine that is driven by combustion of fuel, and the driving force of the engine is assisted by the driving force of the electric motor.
The motor assist apparatus for a vehicle includes the electric motor which can function as a power generator, and includes a rotational position sensor to detect the rotational position of this electric motor. A control means is provided for controlling the motor assist apparatus in relation to a traveling state of the engine so that a high level of performance is attained (such as fuel efficiency, lower values of detrimental components in exhaust gases, and power performance).
Examples of such a motor assist apparatus for a vehicle are disclosed in published Japanese Application Laid-Open Nos. 11-78556 and 11-78558. The motor assist apparatus for vehicle disclosed in published Japanese Patent Application Laid-Open No. 11-78556 includes a preventing member for preventing metal powder produced from the clutch mechanism from invading a motor generator. The motor assist apparatus for vehicle disclosed in published Japanese Patent Application Laid-Open No. 11-78558 includes a shielding member disposed between an engine and a motor generator for shielding electric current and magnetic flux emitted from the motor generator.
However, a motor assist apparatus for a vehicle generates magnetic flux and electric wave noise from the motor stator when the electric motor is being driven and functioning as a power generator. There is a problem that such magnetic flux and electric wave noise may negatively influence other components, such as a rotational position sensor.
Therefore, the motor assist apparatus for a vehicle indicated in each of the above disclosures, includes a shielding member positioned between the engine and the motor generators to prevent electric current and magnetic flux from leaking out of a coil of the motor generator to negatively influence the rotational operation of a crank shaft of the engine which consists of a metal substance, and allows stability of rotational operation.
However, because the above motor assist apparatuses include a position detecting sensor which detects the rotational position of the rotor relative to the stator, magnetic flux and electric wave noise leaking from the stator can negatively influence the position detection sensor and cause noise to occur in a detection signal of the position detection sensor and deterioration of control precision of the electric motor. Additionally, because the above motor assist apparatuses include a separate shielding member, there is the inconvenience of increased number of assemblies and increased numbers of assemblies to assemble.
In order to obviate or minimize the above inconvenience, the present invention provides a magnetism prevention structure of a motor assist apparatus for a vehicle, having an electric motor that can function as a power generator and is driven by electricity, which is directly connected to an engine driven by combustion of fuel, and consists of a motor rotor and a motor stator that is arranged so as to correspond to the motor rotor, comprising: a rotational position sensor that includes a sensor rotor and a sensor stator that is arranged for correspondence to the sensor rotor. The rotational position sensor can detect the rotational position of the motor rotor relative to the motor stator. The motor stator and the sensor stator are each installed in a motor case that is installed in a cylinder block of the engine, and the motor rotor and the sensor rotor are each installed to a rotor installation member that is installed in the crank shaft of the engine. The motor assist apparatus for a vehicle provides a magnetism prevention part integrated into the motor case to prevent magnetic flux and/or electric wave noise from leaking from the electric motor between the motor rotor and the motor stator of the electric motor and a signal line connected to the sensor stator of the rotational position sensor and/or the sensor stator.
In this invention, because the magnetism prevention structure of a motor assist apparatus for a vehicle provides a magnetism prevention part integrated with the motor case to prevent magnetic flux and/or electric wave noise from leaking from the motor stator between the motor rotor and the motor stator of the electric motor and a signal line connected to the sensor stator of the rotational position sensor, this magnetism prevention structure can shield the rotational position sensor and/or signal line from magnetic flux and electric wave noise leaking from the electric motor, without having to arrange for magnetism prevention utilizing other components, or a detection signal of rotational position sensor passing through the signal line, and in addition the rotational position sensor as well, can avoid receiving a negative influence that is caused by magnetic flux and electric wave noise leaking from electric motor. In addition, because the magnetism prevention structure integrates the magnetism prevention part with the motor case, the number of assemblies and the number of assemblies to assemble can be reduced.